Apparatus for de-aeration of liquids



March 24, 1959 R. A. GILBERT 2,878,889

APPARATUS FOR DE-AERATION OF LIQUIDS 2 Sheets-Sheet 1 Filed April 19, 1955 OOOGOC) INVENTOR v RONALD A. GlLsaa-r' 61 479! 54, Mvll ATTORNEY March 24, 19 R. A. GILBERT 2,878,889

APPARATUS FOR DE-AERATION OF LIQUIDS Filed April 19, 1955 2 Sheets$heet 2 4 1m @mnum INVENTOR RONALD A. GlLBERT wzi iwmzig ATTORNEY United States atetiit This invention relates "tth'ap aramror de-seraiifif of liquids and it is an object of the inventionto provide improvedapp'aratusfor the purpose; I

According to the invention a centrifugal separator for de -aerating liquid comprises a separator chamber, preferably in the form of alhollow body of revolution, means for Withdrawing airfrom the upper end of the separator chamber, and'for withdrawing de-aerated liquid from the lower end thereof, and meansfor supplying aerated liquid to the chamber comprising at least one inlet passage ar-' ranged with a substantial tangential component of direction, so as to impart rotary motionto the liquid within the chambenat least one of the walls of "the inlet passage being movable and being resiliently urged towardsv the opposite wall of the passage, so, as to restrict the crosssectional area of the passage'whenthe pressure of liquid inthe passage falls, and thus 'to tend to mairitaina high velocity of flow through the passage and consequent high rotary velocities in the chamber, even when the volumetric rate of flow through the passage falls.

Preferably the movable wall of the passage is consti tuted by a leaf spring, and the leaf spring is preferably pre-stressed with its end in close contact with the opposite wall' of the passage when there'is no flow through the passage. H j t According-to another preferred feature of the invention the separator includes an upper air separation chamber, arranged'above the main chamber, and means for returning the de aeratedli'quid from the upper air-separa tion chamber to the main chamber comprising a conduit leading from theair-separatingchamber and emerging into the inlet passage 'at a point adjacent the thro at there: of formed between the movable wall'and the opposite wall.

chamber arranged to open'when the level of .liquid in the chamber falls to a predetermined level due to the accumulation of air therein.

The separator may include means for admitting addi tional liquidto the main separator chamber, preferably through one or more make-uppass'ages above the level of the inlet passage. I v

The invention is particularly applicable therefore to fuel supply systems of internal combustionengines of the fuel injection type. In such engines it is customary for fuel to be delivered to the fuel injection pumps from the main fuel tanks and for excess fuel to be returned from the injection pumps to an auxiliary tank where air separation occurs,or through an air separator to the main fuel" tanks. It is a further object'of the invention' to provide an improved fuel system which will obviate the necessity for providing a return fuel line for the aerated fuel.

According to another aspect of the invention therefore a fuel system for"an internalconibustion engine of the In 'such case the separato r preferably includes afloat-1 controlled valve in an upper part of the air-separation ice fuel injection comprisesa fuel injection pump, an

air-liquid separator, ,a circulating pump arranged to re;

ceive de-aerated fuel fromflthe separator and to supply, fuel under pressure to the injection pump, and means for returning excess fuel (which is liable .to beaerated) from the fuel injection, pump to the separator, and in-, cluding means for supplying make-up fuel to the circulatory system from'a fuel tank. 1 p

The separator'is preferably as outlined above. ,r The fuel system moreover preferably includes a fuel delivery pump between; the fuel tank. and the separator,

a bypass.return conduit between the twoisides of this. fuel delivery pump, and a control valvein said by-pass conduit arranged to. open oulygwhen the pressure on the outlet side of the pump reaches "a predetermined value, so as to maintainasubstantially constant pressure in the main separator chamber,

The invention may be per forrnedvin various different ways but one specific embodiment as appliedto the fuel supply system of a compression ignition fuel injection type, internal combustion engine, constituting the power unit of an aircraft; will' now be described by way of ex ample with reference to the accompanying drawings in which Figurel is a diagrammatie view of the complete fuel pp y y .1

Figure 2 is a-sectional side elevation through the air separator unit, and

F1gure 3 is a plan viewon thelinesg III--III of Figure 2 with the upper. part of the unit removed.

The fuelsystem includes normal main fuel tanks (not.

shown) from, whieh fuel is delivered to a main supply line 10 bya booster pump (not shown) arranged to main tain a pressure of (say) .IOIbsy/sq. in, in the line. A pri-' mary fuel filter ll is fitted in this main supplyline, and having passed through this filterthe fuel is then delivered to an engine driven fuel delivery pump 12 of the gear type, the outlet side r which is connected to make-up passages13 leading into a centrifugal separator 14. The

inlet and outlet side of the fuel-delivery pump 12are interconnected by a by-pass return conduit 15 which includes a control valve 16 subject on one" side to the pressure 'at the outlet side of the pump 12, and connected also to a diaphragm 1 7 I which. is, acted upon in the opposite direction by thejljair-press ure in' an air. venting line 18, andspring "pressedinto its closed position so as to maintain ,a pressure at the outlet sitle ,of the pump.

12 of say 5 to 10 lbs/sq. infabove the pressure in the air vent'line'18. v v x The centrifugal air ,separ'ator' 14 is provided with an upper air escape port 20, which communicates withthe air vent line 18 referred to, 'arid' a lower de-aerated fuel outlet port 21 whicheommunieates with a second engine,

driven circulating pump 22 (also of the gear type) the outlet side of which isfconnectjed to a, secondary fuel filter 23 throughwhi'cihfthe de-aerated fuel is delivered tothe injection pump or pumps 24 of the engine. Excess fuel (which is liable to be aerated). from the a injection pump or pumps, is returned to the separator 14 through a return conduit 25, and anyjair which may, be

separated in the secondary fuel filter 23'is fed also into this return conduit.

The centrifugal separator 14, as shown in more devt ail in Figures 2 and 3, corn'prises a generally cylindrical Y mainseparator chamber 26 closed at .its upper end by a plate 27 with a small central aperture 28, which communicates with an upper air separation chamber 29 arranged directly above the main chamber 26. The upper partof the cylindricalside wall of the main chamber is 'curved inwards to form a part-spherical head 30, while Patented Mar. 24,1959

arator chamber through four substantially tangential inlet 4 passages 38, so as to impart rotary motion to the fuel within the chamber and thus assist the separation of air. Each inlet passage is provided with a fixed wall and an opposite movable wall, the movable wall being constituted by the free end of a leaf spring'36. Each leaf spring is formed with a length slightly less than a quarter of the circumference of the separator chamber and is secured or rigidly attached at one end to a fixed block 37 mounted adjacent the inner periphery of the annular inlet passageway. The free end of each leaf spring 36 is pro-stressed into contact with the inner face of the next block 37, and the face of each block at the point where the free end of thenextadjacent spring contacts it, is approximately tangential to the inner wall of the separator chamber. The leaf springs 36 may be tapered somewhat from their fixed to their free ends, and their resilience is arranged so as to maintain the pressure in the annular inlet passageway 35 at approximately 35 lbs/sq. in. above the pressure in the separator chamber 26.

It will be realised that if the pressure in the inlet passageway 35 rises above this figure the leaf springs 36 will be deflected inwards so as to admit aerated fuel from the return conduit 25 into the separator chamber 26. If the quantity of excess fuel returned from the injection pumps 24 rises, the leaf springs will be deflected further so as to increase the cross sectional area of the throats of the inlet passages 38, whereas if the quantity of fuel from the pumps falls' the throats of the inlet passages will be reduced. The arrangement thus tends to maintain a substantial and approximately constant flow velocity through the throats of the inlet passages 38, and consequent high rotary velocities in the separator chamber, even when the volumetric rate of flow falls, due for example to increased fuel consumption by the injection pumps.

Make-up fuel for the circulatory system including the separator circulating pump 22, and fuel injection pumps 24, is supplied tothe main separator chamber 26 from the engine driven fuel delivery pump 12. The make-up fuel is supplied to an annular make-up passageway 40 adjacent the upper end'of the separator chamber, and above the annular inlet passageway 35. A series of circumferentially spaced make-up passages 13, which have a tangential component of direction, are provided in the wall of the separator chamber leading from the make-up passageway into the interior of the chamber in the part-spherical portion 30 of the side wall. The make-up fuel is thus caused to rotate with the main mass of fuel in the chamber 26 under the influence of the tangential streams issuing through the inlet passages 38.

The upper air separation chamber 29 is provided, as mentioned above, with an air escape port 20 at its upper end having an intake portion 20a opening into chamber 29. The flow of air through port 20 is controlled by an air escape valve 41 which is actuated by a float 42 mounted within the chamber. Both the main separator chamber 26 and the air separation chamber 29 are normally flooded under the pressure maintained by the fuel delivery pump 12, and air which is separated in the main chamber rises in the central core of the vortex through the central aperture 28 in the upper closure plate and separates out into the upper part 4 of the air separation chamber 29. When the float 42 falls to a predetermined position due to the accumulation of air in the upper chamber, the air escape valve is opened and air is discharged through the air escape port 20 into the air vent line 18. a

A cylindrical fine mesh filter screen 43 is provided in the upper chamber 29 surrounding the float 42 to exclude air bubbles from the annular space 44 surrounding the screen, and a series of passages 45 lead from this annular space downwards through the wall of the main separator chamber into vertical drillings 46 provided in the blocks 37 to which the leaf springs 36 are connected. Each vertical drilling 46 communicates with one or more outlet drillings 47 which emerge at the inner tangential face of the respective block 37 adjacent the point. where the free tip of the next adjacent leaf spring 36 contacts this surface. This point is adjacent the throat of each inlet passage 38, and by venturi effect the reduced pressure at this throat thus draws the deaerated fuel from the air-separation chamber 29 into the streams of fuel issuing through the inlet passages 38.

The fuel supply system also includes a priming line 50 between the primary fuel filter 11 and the secondary fuel filter 23, and a pressure relief valve 51 in this priming line arranged to open when the pressure in the main supply line 10 reaches a predetermined value. The engine driven circulating pump 22 is thus primed as soon as the pressure in the main supply line 10 reaches an appreciable value.

What I claim as my invention and desire to secure by Letters Patent is:

1. A centrifugal separator for de-aerating liquid comprising a hollow body defining a generally cylindrical main separator chamber, means for withdrawing air from the upper end of said chamber, means for withdrawing deaerated liquid from the lower end of the chamber, said body being formed with an annular inlet passageway around said chamber, said passageway being separated from the chamber by an inner peripheral wall between it and the chamber including a plurality of fixed wall portions and movable wall portions, said fixed and movable wall portions being relatively circumferentially spaced around said passageway and alternating with each other around said inner peripheral wall, said movable wall portions each comprising a leaf spring having a cylindrical curvature generally conforming to that of said chamber, said leaf spring being fixedly secured at one end to one fixed wall portion and having a free end extending therefrom circumferentially in overlapping normally contiguous relation with another fixed wall portion, said free end extending radially inwardly of said other fixed Wall portion and cooperating therewith to define a generally tangentially projected variable size inlet passage from said annular passageway into the said chamber and said free end being resiliently radially inwardly yieldably responsive to said fluid pressure in said annular passageway to vary the size of said passage through said passageway, and thus to tend to maintain a high velocity of flow through the passage and consequent high rotary velocities in the chamber even when the volumetric rate of flow through the passage is reduced.

2. A centrifugal separator as claimed in claim 1 including an upper air-separation chamber, arranged above the main chamber, and means for returning the de-aerated liquid from the upper air-separation chamber to the main chamber comprising a passage leading from said air-separating chamber and emerging into said inlet passage at a point adjacent the throat thereof formed between said movable wall portion, and said fixed wall portion.

3. A centrifugal separator as claimed in claim 1, including means for admitting additional liquid to the main separator chamber, through a make-up passage above the level of said inlet passage.

(References on following page) 5 References Cited in the file of this patent UNITED STATES PATENTS Heinrich et a1 Sept. 24, 1940 LOrange Nov. 11, 1941 5 Samiran Nov. 16, 1943 Bidwell et a1 Jan. 10, 1950 6 Davis June 12, 1951 Cline Mar. 25, 1952 Dilworth et a1 June 10, 1952 King Feb. 10, 1953 FOREIGN PATENTS Great Britain Dec. 20, 1938 

